Silver faced slip ring



4 April E. G. COLSON 2,0373157 SILVER FACED SLIP RING Filed Dec. 28,1932 2 Sheets-Sheet 1 INVENTOR Eric 6. 60215072 BY %w% MZ 'ToRNEY April14, 1936. E, LS 2,037,457

SILVER FACED SLIP RING Filed Dec. 28, 1932 2 Sheets-Sheet; 2

FNS ULIATION Z3 32 IN SULiATION INVENTOR TTORNEY Cal Patented Apr. 14,1936 PATENT OFFICE SILVER FACED SLIP RING Eric G. (Jolson, New York, N.Y., assignor to Ford Instrument Company, Inc., Long Island City, N. 'Y.,a corporation of New York Application December 28, 1932, Serial No.649,143,

15 Claims.

'The present invention relates to slip rings of high conductivity withwhich brushes co-act in electricalapparatus whereby electrical circuitsare well maintained through relatively movable elements. The inventiveconcept lies largely in the structure and method of making the slipring, which has been devised to avoid serious defects that have beenpresent in slip rings hitherto constructed to have intended highconductivity, but which has failed to attain this desirable quality.Such failure has resulted in slip rings which are formed mainly of basemetal or alloy and which are provided with annular silver faces solderedthereto in such manner that the solder has been in contact with thesilver faces. The solder has, in these instances, been found topenetrate and permeate the silver to such extent as to contaminate itand rob it of its normally high conductivity. Thus, the very purpose forwhich the silver faces were used on the slip rings has been defeated.

In silver faced slip rings of prior construction, the attachment ofcurrent-conducting leads thereto has been made with the aid of solder insuch manner that the solder used for this purpose has also contactedwith and, therefore, has permeated and contaminated the silver faces,still further depreciating the current conducting quality thereof. Inother forms of slip rings of an earlier period, posts for the attachmentof electrical conductors have had portions riveted to the slip ringswith the rivet heads 'of these portions embedded in the band of silverwhich constituted .the silver face. A common fault in this type ofconstruction is that the rivet heads are frequently not entirely flushwith the exposed silver face, as they are intended to be. Consequently,sparking at and burning of the surface of the silver face of the slipring occurs. An object of the present invention is to avoid theaforementioned defects and ill effects by a construction wherein thesilver face of the slip ring is secured to a foundation annulus in amanner wherein no-solder comes into contact with the silver face so thatthe purity and high conductivity of the latter is maintained.

It is also an object to combine one or more terminal posts to the slipring so that solder used toattach an electrical conductor to theterminal post cannot encounter the silver face of the slip ring andcontaminate it.

Furthermore, by the improved construction, a smooth hard surface isgiven to the silver face, whereby it withstands'wear due to the pressureof a brush bearing against it over a long period of operation, and sothat there is an absence of sparking between the brush and the silverface of the slip ring. v

Other features and advantages appearing hereinafter are, of course, tobe understood as 5 forming part of the present invention.

In the drawings,

Fig. 1 is a sectional view, principally taken on the line Il, of Fig. 2,showing a plurality of silver faced slip rings of the improved typeinstalled in an electrical step-by-step motor, parts being shown inelevation;

Fig. 2 is an end elevational view of the motor disclosing the slip ringsin side view with brushes applied thereto, the bearing mounting themotor yoke being omitted for improved clearness;

Fig. 3 is an enlarged cross sectional view through one side of one ofthe slip rings, illustrating one mode of combining the silver face tothe foundation ring;

Fig. 4 is an enlarged edge view of a portion of the novel slip ring,with a terminal post affixed thereto;

Fig. 5 is another enlarged fragmentary cross sectional view, takensubstantially on the line 5-5, of Fig. 4, through one side of one of theslip rings, but at the point of attachment thereto of one of theterminal posts, portions of the latter being shown in elevation; and

Fig. 6 is an enlarged fragmentary cross sectional view of one side of amodified form of silver faced slip ring.

Referring to the drawings, l represents a portion of the yoke of anelectric motor in which slip rings of the novel type disclosed hereinare installed, while 2 indicates the end bell at the shown end of themotor, the end bell being secured to the motor yoke l by tap screws 3.The illustrated motoris of the step-by-step type in which the field yokeI and-the end bells 2 that are attached to the opposite ends of the yokeform a unitary metallic structure which is mounted at its opposite endsin ball bearings I so that the field structure as a whole may be turned,by unshown means, in accordance with required angular steps.

Integral with the end bell 2 is an inwardly directed annular flange 4,forming a socket 5 inset in which is a ball bearing 6, which, with asimilar ball bearing at the opposite but unshown 5 end of the motor,mounted in similar manner, rotatably supports an armature shaft 1. Faston the armature shaft is an armature 8, which is revoluble between thepole pieces (not shown) on which field coils 9 are mounted.

Formed as an integral part of the end bell 2 is another and outwardlyextending annular flange I0 which forms apocket the inner end of whichis of a slightly reduced diameter to form an annular seat for a circularbase ll of insulating material. A sheet l2 of insulating material isinterposed between the outer face of the end bell 2 and the inner faceof the base ll of insulation and serves as a cover for certain recessesin the latter. An, appropriate number of screws l3 extend through theflat portion of the wall of the end hell 2 and the sheet of insulation[2, these screws being threaded into the insulation base I l to hold thesame in place on the end bell 2.

In advance of the outer face of the insulation base II are a pluralityof concentrically arranged slip rings l4, each of which is mounted onthe insulation base H by means of a number of preferably cylindricalmounting studs I 5. Each stud l5 has a portion ii of reduced diameterwhich passes through and is conformed to a circular hole in thefoundation ring ll of the slip ring. This hole is countersunk, and theend of the reduced portion l6 of the stud is upset to be conformedto andto fill the countersunk portion of the hole, thereby becoming a rivethead which rigidly holds the slip ring l4 against the shoulder formed bythe main and reduced portions of the mounting stud l5. Screws l8 havetheir heads located in recesses in the inner side of the insulation baseI I, the threaded shanks of the screws I8 being screwed into threadedholes in the mounting studs IS. The insulating sheet l2 shields theheads of the screws ill from the end bell 2 and preventsshort-circuiting. Thus, the mounting studs l5 are securely mounted onthe insulation base ll, and in turn hold the slip rings 14 in properrelation thereto and to themselves.

Suitably mounted on an insulating support, as a bar l9 of insulation,are brushes 20, each comprising a rigid metallic member 2| fastened tothe insulation bar l9 by screws 22 and a flexible finger 23 riveted orotherwise combined with the rigid member 2|. The free end of theflexible finger 23 is preferably provided with a silver or silver-platedcontact tip or button 24, which is urged by the spring-like quality ofthe flexible finger 23 into good electrical contact with the slip ring Mwith which it co-acts. A terminal clip 25 is attached by a screw 26 tothe rigid member 2| of each brush 20, and has a bared portion of anelectrical conductor 21 aflixed to it in the usual-manner. An insulatingshield 28 is applied to the insulating bar l9 and projects between theslip rings l4 and the brushes 20.

The structure thus far described sets forth a typical installation ofthe novel slip rings in suitable electrical apparatus, and disclosescertain parts of the invention, but other important features thereofremain to be described. Each slip ring I4 is formed in part of thefoundation ring or annulus ll of any appropriate metal or alloy, such,for example, as brass. As shown in' Fig. 3, the outer and innercircumferential surfaces of the foundation ring I! are bevelled inwardlyfrom the opposite edges of the vertical outside surface 29 of the' ringI! to an adequate extent for a purpose disclosed later, thereby formingan inwardly inclined face 30 and a circular shoulder 3| on each of theouter and inner circumferential surfaces of this ring. Extending fromthe shoulders A 3| these circumferential surfaces of the foundation ringI I are parallel as they extend to the vertical inside surface 32 of thering H.

The vertical outside surface 29 and the inwardly inclined surfaces 30 ofthe outer and inner circumferential surfaces of the foundation ring I!are preferably silver-plated so as to constitute excellent electricalcontact surfaces. An annular relatively thin piece of silver 33 ofgreater width than the circular outside surface 23 is applied to thelatter and the marginal borders of the silver piece 33 are spun over tolie against the inwardly inclined surfaces 30 of the ring H. The processof applying the thin annular silver piece 33 to the foundation ring I!is such that the silver facing 33 is at all places in such thoroughlyintimate contact with the enclosed portions of the foundation ring llthat the silver face 33 and the foundation ring l'l correspond, ineffect, to'a unitary electrical current-conducting element.

During the application of the annular silver facing 33 to the foundationring II, this silver face of the slip ring I4 is economically burnishedby the spinning operation and at the same time it acquires a smooth,polished surface that is quite hard. Accordingly, there is an absence ofsparking as the slip rings l4 revolve relatively to the brushes 20, andthere is also resistance to wear whereby the slip rings have long life.

To provide a good path for electrical current between the slip rings l4and the electrical means with which they turn, as the coils 9 of themotor field, terminal po,sts 34 are affixed to the slip rings, say, oneto each slip ring, although any desired number of terminal posts may besecured to such ring. The attachment of the terminal post 34 to the slip'ring I4 is made prior to the application of the silver facing 33thereto so that circular continuity of smoothness of the silver face ofthe slip ring is maintained constant.

Reference to Fig. 5 shows that at the place of attachment of theterminal post 34 to the slip ring the brass foundation ring I! isprovided with a hole extending from one vertical side to the other ofthe ring, which hole is countersunk from the outside vertical surface ofthat ring. The terminal post 34 is provided with a portion 35 of reduceddiameter that extends in cylindrical form through the hole in thefoundation ring I! and into the countersunk portion of this hole whereit is converted into a frusto-conical head 36 that conforms to andsubstantially fills the countersunk portion of the hole. The shoulder 31formed by the main and reduced cylindrical portions of the terminal post33 is thus held tightly against the vertical inside surface 32 of thefoundation ring l1, and the terminal post 34 is thus rigidly combinedwith the latter.

At its unattached end the terminal post 34 is provided with a saw-cut 38of suitable width, in which is laid the bared end 39 of an electricalconductor 40. The saw-cut 38 is otherwise filled with solder 4| securelyattaching the conductor 40 to the terminal post. As shown in Fig. 1, theconductor 40 goes to a field coil 3, of the motor, though in otherelectrical apparatus it may be connected to any current-conveyingelement.

From the preceding description it is clear that the silver face 33 isapplied to and interlocked with the brass, or other, foundation ring I!without the use of solder, or any other fusible alloys, that wouldpenetrate and contaminate the silver face, and consequently the silverforming the face of the slip ring is possessed of its maximum purity andhigh degree of conductivity. Also, the outer facing 33 and thefoundation ring I! are combined with a silver to silver contact, and theattached end of the conductor." is secured to the the silver face 33 ofthe slip ring so that the silver face is not penetrated and contaminatedby the solder 4| used to attach the bare end 39 of the conductor to theterminal post 34. If desired, the end of the conductor may be attachedto the terminal post by mechanical fastening means. Moreover, the spunover marginal edges of the silver face 33 require the shoulders 3! ofthe foundation ring to be retracted from the brushengaged surface of theslip ringsufficiently to prevent any jumping of the electric current immediately to the foundation ring H.

A modifiedform of the silver faced slip ring is shown in Fig. 6, whereinthe silver' face 33' has reversely bevelled sides 30' that are inclinedin the opposite directions to which the corresponding sides 30 offoundation ring ll of the first described form of slip ring areinclined. In the form of Fig. 6, the foundation ring ll of, say, brass,has an originally rectangular but subsequently bevelled groove 42, thegroove-forming flanges 43 being forced inwardly to grip and retain thesilver ring 33'. This arrangement has the virtue of being simple inconstruction but ordinarily requires the silver ring to be of greaterthickness than the silver facing 33 of the form shown in the otherviews. Due to the convergence of the bevelled sides 30' toward thebrushengaged surface of the silver ring 33', shown in Fig. 6, thissurface is narrower and is suited to brushes of small contact area,While the surface 33 of the ring shown in cross section in Fig. 3 iswider and better adapted for engagement by comparatively wide brushes ofrectangular cross section. In either form of slip ring, however, thesilverfacing is securely affixed to the foundation ring with a dovetailconstruction, and Without the use of solder or other fusible alloys.

While the novel slip rings herein disclosed have been shown anddescribed as being installed in one type of motor, it is to beunderstood that they maybe employed in other types of motors and, infact, in any electrical apparatus wherein there are relatively rotatableparts between which an electrical connection, or connections, arerequired. Also, if desired, the silver facing may be applied to theouter circumferential surface of the foundation ring, instead of beingaffixed to a vertical side thereof, as in the illustrated form. Thisobvious alternative form would be the natural arrangement where aplurality of slip rings are arranged side by side, as in certainwell-known types of dynamoelectric machines.

The herein described silver cup rings are simple and reliable inconstruction and service-giving qualities, as well as being relativelyinexpensive to manufacture, and it is obvious that changes andalterations may be made in the particular form of construction of theslip ring without departing from the spirit of the invention as definedin the appended claims.

I claim:--

1. A slip ring comprising a metallic foundation ring, and a separatecontinuous current-conducting annular facing in immediate contact withan annular surface of said ring, part of the external surface of saidfacing forming an electrical contact surface, said ring and facing beingformed to effect a dovetail connection between themselves.

2. A slip ring comprising a metallic foundation ring, and a separatecontinuous currentconducting annular facing in immediate contact with anannular surface of said ring, part of the external surface of saidfacing forming an electrical contact surface, said foundation ring andfacing being formed as annular co-acting dovetail connection elementsone of which has marginal flanges retentively bent over portions of theother.

3. A slip ring comprising a metallic foundation ring, having a portionthereof including an uninterrupted annular surface of said foundationring formed as an annular dovetail member, and a continuous relativelythin annular facing of high electrical conductivity having an innersurface in electrical contact with said annular surextending over theannular dovetail-memberforming portion of said foundation ring inconformity to receding sides thereof.

5. A slip ring comprising a foundation ring having a portion thereofincluding an annular surface of said foundation ring formed as anannular dovetail member, the same being plated with metal of highelectrical conductivity, and

a relatively thin annular facing of high electrical conductivity formedas a co-acting dovetail member lying in intimate contact with the platedportion of said foundation ring, said facing having marginal edges spunover opposite sides of the annular dovetail-member-forming portion ofsaid foundation ring.

6. A slip ring comprising a metallic foundation ring and anelectrifiable annular facing covering an annular surface of saidfoundation ring, one having portions bent over and completely exteriorto opposite sides of the other, said portions extending inwardly towardeach other so that the free ends of said portions are separated by anamount less than the width of said annular surface of said foundationring, whereby said annular facing is held in electrifiable contactagainst said annular surface of said foundation ring.

7. A slip ring comprising a metallic foundation ring having an annularsurface and opposite bevelled surfaces exterior to said ring andinclined inwardly from said annular surface forming an annular dovetailtongue, and a relatively thin silver annulus in continuous parallelismand intimate contact with said annular surface and having spun overmarginal edges, said silver annulus and its said edges forming adovetail groove receiving said dovetail tongue and constituting themeans of attachment of said silver annulus to said foundation ring, theouter surface of said silver annulus being burnished and hardened.'

8. A slip ring comprising a foundation ring, a relatively thin silverfacing in parallelism with an annular surface of said foundation ringand interlocked with the latter, and. a terminal post rigidly afflxed tosaid foundation ring and provided with electrical conductor attachingmeans removed from said silver facing.

9. The combination with electrical apparatus having a current conveyingcontact and an electrical conductor, of a slip ring engaged by saidcontact and comprising a foundation ring, a relatively thin facing ofhigh electrical conductivity in parallelism with an annular surface ofsaid foundation ring and interlocked with the latter, a terminal postrigidly aflixed to said foundation ring and provided with a recessremoved from said foundation ring and facing in which recess a bareportion of said conductor lies, and a deposit of fusible metallicsubstance in said recess combining said conductor and terminal post.

10. The combination with electrical apparatus having relatively movableparts one of which carlies a current-conveying contact and the other ofwhich is provided with electrifiable means and an electrical conductorconnected therewith, of an insulating base mounted on the last namedpart, a slip ring mounted on said base and comprising a foundation ringand an annular facing of high electrical conductivity thereforinterlocked therewith and engaged by said contact, a terminal postrigidly affixed to said foundation ring and provided with a recess awayfrom said ring in which recess said conductor lies, and a fusiblemetallic substance in said recess combining said conductor and terminalpost.

11. The combination with electrical apparatus havingrelatively-rotatable parts one of which carries a current-conveyingcontact and the other of which has electriflable means provided with aconductor and a member containing a pocket, of an insulating basemounted on said member in the pocket thereof, a slip ring mounted onsaid base and comprising a foundation ring and an annular facing of highelectrical conductivity therefor interlocked therewith and engaged bysaid contact, a terminal post afiixed to said foundation ring recessedfor and receiving said conductor, and a fusible metallic substancecombining said conductor and terminal post.

mounting said slip rings on and insulating the same from said secondnamed part, said slip rings individually comprising a foundation ring,an annular facing therefor of relatively high electrical conductivityinterlocked therewith and engaged by one of said contacts, and terminalposts rigidly affixed to the respective foundation rings and providedwith recesses remote from said facings, said conductors having terminalportions in said recesses combined with said posts by fusible metallicmaterial.

13. In combination, an electrical conductor, a slip ring comprising afoundation ring provided with a hole therethrough expanded near anannular surface of said foundation ring, a relatively thin facing ofhigh electrical conductivity in parallelism with and intimately engagingsaid annular surface, said facing being spun into interlocked relationwith said foundation ring, a terminal post having a portion of reduceddiameter extending through said hole and having a head fitting theexpanded portion of said hole, said post having a recess at a pointremoved from said facing in which recess a part of said conductor lies,and a fusible alloy in said recess uniting said conductor and post.

14. A slip ring including a metallic foundation ring having a pluralityof faces and a pair of annular recesses each of which is located betweena pair of adjacent faces of the ring and is formed with an inwardlyinclined face and a circular shoulder, and a metallic facing held incontact with the face of the ring located between the recesses by havingthe marginal portions of the facing in engagement with the inwardlyinclined faces of the recesses.

15. A slip ring including a metallic foundation ring having a pluralityof faces and a pair of annular recesses each of which is located betweena pair of adjacent faces of the ring and has an inwardly beveled faceand an annular shoulder and a metallic facing having its marginalportions in engagement with the inwardly beveled faces of the recesses,whereby the facing is held in contact with the face of the ring locatedbetween the recesses.

ERIC G. COL-SON.

